In lawn care, groundskeeping and landscape care, there is a great need for plant or weed control without the application of herbicides or toxic substances.
Reducing the use of pesticides for weed and plant control has become an issue of national importance. Ground water is vitally important and the use of herbicides to prevent weeds from growing in homeowner and commercial lawns adversely impacts the quality of ground water. Most herbicides are persistent, soluble in water, and ingestion at high toxicity levels can be carcinogenic, affecting the human nervous system and causing endocrine disruption.
To protect water quality, simple removal methods not relying on pesticides are widely sought. Ninety-five percent of fresh water on earth is ground water. Ground water is found in natural rock formations called aquifers, and are a vital natural resource with many uses. Over 50% of the USA population relies on ground water as a source of drinking water, especially in rural areas.
In the USA, concerns about the potential impacts of herbicides on human health, as well as on terrestrial and aquatic ecosystems, have led to a wide range of monitoring and management programs by state and federal agencies, such as the U.S. Environmental Protection Agency (USEPA). For example, atrazine is a toxic, white, crystalline solid organic compound widely used as an herbicide for control of broadleaf and grassy weeds, and has been detected in concentrations problematic for human and animal health.
Mechanical and thermal phenomena marshaled against undesirable plants by prior art devices, methods and teachings are not effective, and this is due to the natural robustness of plants, due to their physiology and responses to natural trauma. The role of repair, regrowth, and the beneficial effects of soil-borne microbes all play a role in the hardiness of plants to prior art thermal and mechanical methods for plant control.
Referring to FIG. 1, a schematic representation of a typical plant root is shown in cross section. In root R illustratively shown, a central xylem layer X is shown surrounded by a phloem layer P. The xylem layer X (see definitions) operates to transport water and when needed, healing substances that repair wounds, such as burn wounds or severing, lacerations, and the like. Phloem layer P is typically a living transport layer which transports organic substances such as glucose and other sugars, amino acids and hormones. Surrounding phloem layer P is cortex C, which is in turn surrounded by an epidermis E1 as shown.
Root R is typically surrounded by earth or soil G. FIG. 2 shows a schematic of a plant root cross section surrounded by rhizospheric soil in the immediate vicinity of the root, or on or the root itself.
It is well known that soil-borne microbes interact with plant roots and soil constituents at the root-soil interface. This produces a dynamic environment of root-microbe interactions known as the rhizosphere, whose character and effect on the life of a plant varies widely with differing physical, chemical, and biological properties of the root-associated soil. Root-free soil without such organisms is known as bulk soil. Releasing of root exudates, such as epidermis flakes and other secretions, is sometimes called rhizodeposition and provides growth material, structural material or signals for root-associated microbiota. These microbiota feed on proteins and sugars released by roots. Protozoa and nematodes that feed on bacteria are also present in the rhizosphere, and provide nutrient cycling and disease suppression by warding off pathogens. Reference: Oxford Journals Journal of Experimental Botany Volume 56, Number 417 Pp. 1761-1778, hereby incorporated in this disclosure in its entirety.
The balance of populations in a healthy symbiotic rhizosphere is important, because, in part, the bacteria which provide disease suppression interact with pathogens in a variety of ways, including mechanisms of antagonism, such as by competition for nutrients, parasitism, predation and antibiosis. Fungi, too, can be involved, and their actions, when turned from symbiotic to antagonistic, can be lethal for a plant.
There are three separate, but interacting, components recognized in the rhizosphere: the rhizospheric soil, the rhizoplane, and the root itself. The rhizosphere is soil influenced by roots via release of substances that affect microbial activity. The rhizoplane is the root surface, including the strongly adhering soil particles. The root itself also participates, because certain micro-organisms, known as endophytes, are able to colonize root tissues.
Now referring to FIG. 3, a schematic representation is shown of a plant root acted upon by heat, cutting and damage (shown), which is the subject of this invention. But as shown in FIG. 4, much of the possible actions using heating, cutting and damage are tolerated by a plant as being natural trauma for which there are repair and regrowth processes.
FIG. 5 shows partial cross sectional, partial surface view of a plant in soil, with a root structure in soil, and is given merely to be illustrative. Plant Y is shown with root R established in earth or soil G under a ground plane Z. Plant Y possesses the root features as given in FIG. 1, and other components such as leaf or leaves L as shown.
FIGS. 6-21 show prior art eradication processes or natural trauma which are not effective for plant control, using views similar to that of FIG. 5. For example, in FIGS. 6-9 showing pulling to induce tensile failure such as by natural events like feeding of cows and other ruminants. FIG. 7 shows a tensile failure (shown) in root R occurring below the ground surface Z. FIG. 8 shows the root R after the body of plant Y as previously shown has been removed, leaving a stumped root as shown. FIG. 9 shows Regrowth from root R, which is a common response to such a natural trauma.
FIGS. 10-11 show a similar response to a severing action or cut, with FIG. 10 showing schematically a CUT using a dashed line, which can represent gnawing or eating by an animal, or cutting using a cutting tool or machine such as a chain saw. For example, the top 5 cm (2 inches) of root can be gnawed or cut away. The result, a response by a healthy plant is shown in FIG. 11, where Regrowth is again shown, where new shoots are induced by hormonal and other changes in the plant.
FIGS. 12-14 show the result of burn or fire treatment to the plant root and surrounding soil. Many methods for plant control in the prior art employ fire, steam, or other methods to burn or overheat plant structures. FIG. 12 shows schematically a FIRE impinging upon plant Y and/or root R, with FIG. 13 showing a burned root R with a burned stump as shown, such as might be found after a forest fire, with combusion byproducts, volatilized proteins or smoke 88 rising from the stump as shown. Even obliterating plant Y above ground in this manner typically results in the response shown in FIG. 14, which shows Regrowth similar to that shown in FIGS. 9 and 11.
FIGS. 15-16 show a response to similar healable trauma in the form of surface trauma delivered to plant root epidermis and cortex. FIG. 15 shows lacerating or abrasion of the epidermis and possibly the cortex of root R, such as by a gnawing animal, or by trauma delivered by a shovel blade or other tool (shown, Surface Trauma to Cortex). Repair typically ensues, as shown in FIG. 16 where the root has been violated, using known repair processes studied in the botanical arts.
The rich and robust response mechanisms found in plants to deal with trauma can even deal with trauma that are not so obviously emulating natural events, such as the hot needle wound shown illustratively in FIGS. 17-18. FIG. 17 shows a Hot Needle Wound (shown) where a hot needle pierces root R, possibly right to xylem layer X. The problem with this type of trauma is it is well defined and lends itself to repair using latex or other healing substances that are dispatched to the scene of the wound, usually using xylem layer X to transport needed enzymes and healing tars. The result is shown in FIG. 18 as a Repair to the root structure, restoring function for plant survival.
Because of the ability to withstand forest fires and lightning strikes, most plants do not respond in large numbers to application of heat as given in the prior art. FIG. 19 shows a prior art heat applicator disclosed in U.S. Pat. No. 1,843,187 to Wood, employing a heater H in thermal communication with an application rod as shown. As will be discussed below, the shape of the rod is not appropriate for effecting the present invention, and Wood '187 does not teach or suggest the methods or devices taught here.
Application of thermal contactors or applicators such as shown in FIG. 19 have not met with success (see discussion below). Prior art eradicator 28 as shown in FIG. 20 is brought to bear upon plant Y and root R, allowing for Heat Applied to Root Crown (shown). Much of the heat in these types of devices is wasted through heat losses to air and soil (see discussion for FIG. 41), in part shown, Waste Heat Applied to Soil. The result, as given in FIG. 21 is ineffective or can be beneficial or stimulative, with repair to root R often making the root more robust to future similar trauma.
As can be seen from the above discussion, the delivery of trauma which resembles natural trauma (e.g., application of heat alone) is not effective, because the plants so treated tend to heal and regenerate, probably as a result of centuries of evolution.
For example, in U.S. Pat. No. 5,189,832 to Hoek et al., gas-fired burners are directed at nuisance vegetation along a ground plane. This and other prior art methods which burn or heat plant parts usually fail, because plants have evolved to tolerate, and sometimes be stimulated by, forest fires and lightning strikes.
Moreover, merely severing a plant, such as using a chain saw to cut vegetation also does not work. Cutting or severing root stock often allows new growth to emerge from the root. For example, in U.S. Pat. No. 5,305,584 to Hessabi, a flat spade-like heated element is used to sever vegetation. The active injuring element severs, but does not inflict a specific unnatural injury as taught here, and in particular, the heated rod of Hessabi '584 of FIG. 6 is not effective for long term weed control.
As discussed, cutting plant roots and warming roots are not particularly effective for weed or plant control in most cases. With plants having evolved for regrowth despite severing roots, or forest-fire related fire and heat damage, prior art mechanical and thermal methods have low success rates.
This is true despite assertions made in prior art patent publications. For example, U.S. Pat. No. 1,399,529 to J. R. Stewart states that with his invention the application of the intense heat is directed upon the crown of the weed root and it is immediately killed. (See Col 1, lines 23-26). However, this method has been shown to be ineffective, with maximum success rates obtained on the order of 25 percent. Moreover, the teaching of Stewart '529 does not address any particular wound to a plant root. A device is given which employs a tip that terminates in a sharpened point 13. In using the device this point is thrust into the ground so that the crown of the weed root is in contact with the metal surface of the point (see Col 2 lines 71-75). Using such a device having a conical tip (such as shown in FIG. 19), it is not easy to stab a root manually, as the tip tends to side-swipe or miss stabbing engagement with a plant root.
Speed of application and overall success rate are very important, and other prior art devices fall short in satisfying these two considerations. For example, U.S. Pat. No. 2,051,684 and also U.S. Pat. No. 1,982,646 to Dick do not teach or suggest any root stab, only teaching simple application of heat to a plant root. Similarly, U.S. Pat. No. 1,843,187 to Wood does not suggest a stab capability or heat or temperature details that would allow a special trauma that is unhealable in most cases. Although Wood '187 teaches use of a needle, it appears that this form is used for the purpose of driving the needle into the ground (see Wood '187 claim 2), so as to be proximate a plant root for contact heating purposes only.
Thermal considerations play a role and the prior art is largely silent on the role of temperature and wound shapes. Generally, the prior art gives no teaching as to how to inflict damage that is unhealable to a plant.